Sewage treatment system

ABSTRACT

A concentrator system having a large diameter vacuum drum over which an endless filter media screen is trained. The endless screen has an overall length substantially greater than the circumference of the drum and is trained over an idle roller horizontally displaced from the drum. Solid containing liquid slurry or sludge is flowed onto the generally horizontal upper reach of the screen adjacent the roller by horizontal feed. As the screen carries the slurry or sludge away from the feed end, gravity filtering of liquid through the screen takes place. When the screen passes over the drum, vacuum de-watering further reduces the liquid content.

United States Patent Goodman et al. 1 Dec. 5', 1972 I 5 1 SEWAGETREATMENT SYSTEM 3,492,200 1/1970 McKie et al. ..l62/358 x Inventors: iG0odman; B. 3,109,219 ll/1963 DeBell et al. ..L ..l62/DlG. l

gins, both of Overland Park, Kans. v I v Primary ExammerReuben Friedman[73] Assignee: Ecodyne Corporation, Ch1cago,lll. v Assistant Granger[22] Filed: Jan. 11, 1971 Attorney-Hume, Clement, Hume & Lee, lJtd. [21]Appl. No.: 105,189 [57] -ABSTRACT A concentrator system having a largediameter [52] US. Cl ..2l0/40l vacuum drum over which an endless filtermedia [51] 11 11. Cl. ........B01d 33/14 Screen is trained The endlessScreen has an overall [58] new of Search "210/54, 162/336 lengthsubstantially greater than the'circumference of 162/358 1 the drum andis trained over an idle roller horizontally displaced from the drum.Solid containing liquid slurry [5 6] References cued or sludge is flowedonto the generally horizontal upper UNITED STATES ATENTS reach of thescreen adjacent the roller by horizontal feed. As the screen carries theslurry or sludge away 3,399,111 8/1968 Beaurnont et al ..162/358 X f dthe f d end, gravity filt i f liquid through 2,895,614 7/1959 Kofnlme210/401 the screen takes place. When the screen p'assesover 2,916,14512/1959 Kaiser 210/401 t drum vacuum de watering further reduces h2,568,420 9/1951 Thomson.... ..210 401 liquid content 2,435,467 2/1948Spencer l62/DlG. l 2,907,388 lO/l959 Seaman 162/336 6'Claims, 5 DrawingFigures e z; final/mm 2011/5 VAC/MM m mum/m2 mew/M m rm 5' 75' 75MSEWAGETREATMENT SYSTEM BACKGROUND OF THE INVENTION This inventionrelates in general to the treatment of solid containing liquids and moreparticularly with the concentration of solids from a liquid. It dealsspecifically with the concentration, for disposal, of sludges which arethe product of sewage aeration, sedimentation or chemical precipitationor the like.

A wide variety of sludge concentration systems, as

they will herein be referred to, are presently available in the UnitedStates. Some of these systems rely primarily on the force of gravity todraw liquid from the sludge through a filter media and concentrate ordewater the sludge, while others employ a vacuum drum over which afilter media is passed and into which the liquid filtrate is drawnthrough the media. There are, in addition, a few systems extant whichemploy both gravity and a vacuum arrangement to draw liquid from asludge through a filter media to de-water or concentrate it.

Exemplary of the most effective gravity-type system is that illustratedin the applicants own Goodman et al. US. Pat. No. 3,531,404, issuedSept. 29, 1970, titled SEWAGE TREATMENT SYSTEM. This system employsanendless filter media screen extending in generally horizontalrelationship between rollers. Liquid filtrate drains downwardly throughthe screen from the high liquid content sludge deposited on it as thescreen moves horizontally.

The vacuum drum sludge treatment concept is best understood by referenceto the drawings where a simplified cross-sectional view of aconventional vacuum filter system is shown. This drum type vacuum filtersystem consists of a cylindrical drum A which rotates partiallysubmerged in a sludge tank B. Afilter media screen C covers the filterdrum and retains the-solids from the sludge while passing liquid intothe drum as the filter media moves through the sludge cake pick-up zoneD. As a section of the drum A rotates into the zone D, appropriatevalving within the drum A creates a pick-up vacuum in that section ofthe drum and liquid flows from the sludge through the filter media intothe drum where it is disposed of through suitable piping.

The solid portion of the sludge retained on the filter media C as itdeparts the feed tank B and enters the drying zone F, where much of theremaining free water is removed. The filter media screen C then passes adischarge roll G where the sludge cake is removed, after which thefilter media is washed with spray water, as at H, before being returnedto the filter drum over a return roller J.

In contrast to both of the aforedescribed systems, one system whichemploys both vacuum and gravity concepts in de-watering sludge ismanufactured by Ametek, Inc./Process Equipment, East Moline, Illinois,under the trademark FlLT-R-BELT. This is essentially a horizontal filtermedia screen arrangement, with the added feature of vacuum boxesdisposed beneath the horizontal run of the filter screen. Thesehorizontal vacuum boxes assist in drawing the liquid filtrate throughthe media from the liquid laden sludge deposited on the moving screen.

. 2 SUMMARY OF THE INVENTION The present invention is embodied in animproved concentrator system for de-watering and concentrating thesolids in a high liquid content slurry or sludge or the like. A primaryobject of the invention in its preferred form is to provide an improvedconcentrator system which advantageously employs both a vacuum andgravity in de-watering and concentrating sewage sludges to solidconcentrations that will allow the sludge to be either burned ordisposed of by burial in the case of a non-combustible sludge.

The foregoing and other objects are realized in .accord with theinvention by providing a concentrator system including a filter mediacomprising a fine mesh, mono-filament screen, having openings in therange of 50-500 microns, which is trained around a rotatable drum. Theendless screen is longer than the circumference of the drum so thatasection of substantial length extends generally horizontally toward thedrum into tangential relationship at the top of the drum from a pointspaced'fr'orn the drum 'where it is trained over an idle roller. Highliquid content slurry or sludge flows horizontally onto the screenthrough a distribution trough adjacent the aforementioned idle roller.

The screen is continuously moving away from the distribution trough sothat clean screen is continuously being exposed to the incoming slurryor sludge. As the screen advances, gravity de-watering of the sludgetakes place along the substantially horizontal screen section, prior toengaging the drum, in a gravity dewatering zone. The filtrate thatdrains from this zone is caught by a filter pan and disposed of throughan effluent drain. e

The screen carrying the partially de-watered solids rotates around thedrum through a vacuum de-watering zone. The drum around which thefiltermedia screen is trained is divided into a number of sections, eachof which is connected to an automatic control valve by internal piping.The automatic control valve regulates the application of vacuum to thecompartments of the drum and, as a section of the drum enters the vacuumde-watering zone, the valve applies vacuum to that section to drawadditional liquid through the screen and effect further de-watering.

The water which is removed in this manner is discharged from the drumthrough piping in the drum. The cake of solids is removed from thescreen as it passes out of the vacuum de-watering zone and then thescreen is washed before returning to the distribution trough.

BRIEF DESCRIPTION OF THE DRAWINGS The invention, including itsconstruction and method of operation, taken with other objects andadvantages thereof, is illustrated more or less diagrammatically in FIG. 4 is a front elevational view of the unit, as seen from thedistribution trough end; and

FIG. 5 is a rear elevational view of the unit, as seen from the drumend, illustrating the vacuum pipe and valve system of the drum.

DESCRIPTION on THE PREFERRED EMBODIMENT Referring now to the drawings,and particularly to FIGS. 2-5, a sewage treatment unit incorporating asludge concentration system embodying features of the present inventionis illustrated generally at 10. The unit includes a box-like body 11including a floor 13, identical side walls 14, a front end wall 15, anda back end wall 16. The floor and walls are joined at adjacent edges inliquid tight seams and leave an open top.

The side walls 14 of the open top body 1 I extend the full height of thefront wall 15 for approximately onethird the length of the body, fromwhich point they are inclined downwardly to terminate at the same heightas the relatively short back wall 16. The result is abody 11 which hasrelatively high side walls adjacent its front end, sloping to relativelylow side walls adjacent its back end. This configuration is designed toaccommodate a vacuum drum assembly inside the body and a filter screen21 which extends from the drum assembly 20 to an idle roller assembly 22adjacent the front wall 15 of the body 11.

The vacuum drum assembly 20 includes a drum mounted for rotation aboutthe horizontal axis of its center shaft 31 on drum support horses orstanchions 32. One end of the shaft 31 is journalled for rotation in aconventional bearing 35 affixed to the top of the stanchion 32 while theopposite end of the shaft 31 is journalled in an automatic distributorcontrol valve 36 mounted atop the stanchion 32.

The drum 30 includes oppositely disposed circular drum ends 40 rigidlysecured to the shaft 31. Extending between the drum ends 40 and formingthe annular outer periphery of the drum is a cylindrical drum wall 41.The drum ends 40 are each fabricated of a relatively thin sheet metal ina well-known manner and braced by a plurality of radially extendingpartitions 45. They are impervious to the passageof liquid. On the otherhand, the cylindrical outer wall 41 of the drum 30 contains a myriad oftiny perforations designed to facilitate the passage of liquid throughthe wall.

The drum 30 is separated into a plurality, six in the presentillustration, of circumferentially spaced chambers 47 by radiallyextending partitions 45 disposed between the shaft and the inner surfaceof the cylindrical drum wall 41. These partitions extend the length ofthe drum 30, between the ends 40 and are, in the manner of the ends 40,impervious to the passage of fluids.

Each of the compartments 47 contains a generally L- shaped pipe 52 whichextends from its open free end 53 adjacent the drum wall 41 through acorresponding end 40 of the drum 30 into the valve 36. in the valve 36,the pipes 52 open through corresponding ports in a rotatable valve plate54. The valve plate 54 rotates in sealed relationship against a fixedvalve plate 55 having a single aperture extending through it. Theaperture in the fixed valve plate 55 is so arranged that it places thevacuum chamber 57 of the valve 36 in communication with two adjacentpipes 52 when the chambers 47 in which these pipes 52 are disposed passthrough a vacuum de-watering zone, in a manner hereinafter discussed indetail. Suffice it to say for the moment that a vacuum maintained in thechamber 57 from asuitable vacuum producing source through an externalpipe 58 is made effective in successive ones of the chamber 47 as thedrum 30 rotates so that the vacuum is effective in a prescribedde-watering zone on the periphery of the drum to aid in de-watering thesludge being treated according to the invention.

The filter media screen 21 is trained around the cylindrical outer wall41 of the drum 30 and the idle roller assembly 22, as has been pointedout. The screen 21 is endless and preferably made of a polyester fabricsuch as DuPonts Dacron. The fabric is, at any rate, of a mono-filament,mesh construction. In the form used herein, it has openings of amoderate size in the 50 500 micron range. it should be pointed out atthis point that the term mono-filament as used in this application todescribe the screen material, is also intended to be inclusive of wovenmaterials wherein the strands which are woven to form the'mesh are, intheir own right, actually formed of multiple fibers or the like. Thus,mono-filament in the glossary of this application means single strand.

The idle roller assembly 22 comprises a conven tional, smaller diameteridler roller 60 affixed to a horizontally disposed shaft 61. The shaft61 is journalled, at its ends, in horizontally adjustable journal blocks64 mounted on the side walls 14 of the body 11.

With the filter media screen 21 trained over the roller 60 and the drum30, the idler roller assembly 22 is adjusted by moving the journalblocks 64 to draw the screen taut in a generally horizontal, althoughslightly inclined upper run 70, and a lower run 71 which is inclined ata substantially greater angle to the horizontal. Both the upper run andthe lower run 71 of the screen 21 extend into tangential relationshipwith the drum 30. The screen 21 is constantly driven with the drum 30and the roller 60 in a clockwise direction by a suitable power sourceand a drive shaft connection (not shown) to the drum shaft 31.

Mounted on the front end wall 15 of the unit body 1 1 is a sludge feedcomplex 75 which delivers liquid-laden sludge to the filter media screen21 on its upper run 70 adjacent the idle roller 60. The feed complex 75includes a sludge inlet pipe 77 connected to a suitable source of liquidladen sludge (not shown). The sludge inlet pipe 77 feeds upwardly into arelatively wide sludge well 78 which extends above the level of the endwall 15 and the side walls 14 of the unit body 11. Opening inwardly ofthe body 11 from the feed well 78 and its uppermost end is a sludgedistribution trough 80. The floor 81 of the distribution troughterminates at an inner edge 82 over the screen run 70 adjacent theinnermost extremity of the roller 60, as seen in FIG. 4.

The side walls 85 of the trough 80 have baffles 87 extending therefromon opposite sides of the screen run 70 toward the drum 30. As seen inFlGS. 3 and 4, these side baffles 87 terminate at their innermost ends88 approximately mid-way in the screen run 70 to the drum 30 from theroller 60. The baffles are designed to prevent the high liquid contentsludge feeding onto the screen run 70 adjacent the roller 60 fromrunning off the sides of the run.

Underneath the drum 30, roller 60 and screen 21 trained therearound, isa filter pan 90. The pan '90 extends the length of the body 11, issupported from the floor 13 thereof, and includes a long downwardlyinclined section 91 from the front wall 15 of the body to the floor 13immediately under the drum and a short upwardly inclined section 92 fromthis point underneath the drum 30 upwardly to the top of the short backwall 16. A pair of drain ports 95 are formed in the bottom of the filterpan 90.

Secured to the back wall 16 of the bodyv l l is a sludge scraper blade97. The transversely extending working edge 98 of the blade 97 extendsinto immediately adjacent relationship with the screen 21 trained aroundthe drum 30 and it is designed to scrape de-watered sludge from thedrum.

Attention is now directed to FIG. 1 for a brief explanation of theoperation of the unit 10 incorporating the sludge concentrator systemembodying features of the invention. Here, in diagrammatic illustration,it will be seen that liquid-laden sludgeis fed up through the sludgewell 78 and out of the trough 80 onto the screen run 70. The sludgethusf'loads horizontally onto the screen run 70. The side baffles 87contain it so that the high liquid content sludge stays on the screenrun 70.

The screen moves away from the distribution trough 80 toward the drum 30through a gravity de-watering. Drainage of liquid from the sludge takesplace by gravity in this zone and a sludge cake is formed. The liquidfiltrate which drains from the gravity de-watering zone is caught in thefiltrate pan 90 and exits through the ports 95.

When the partially de-watered sludge reaches the drum 30, it enters thevacuum'de-watering zone. The automatic valve 36 is effective, by virtueof the porting in the valve plates 55 and S4, to apply vacuum toadjacent compartments only during the portion of their rotation whereinthey are passing through the vacuum de-watering zone. The sludge cake isfurther dewatered as it passes through this zone by vacuum applied tothese sections. The water is removed from inside the drum through thepipes 52 which are drawing air out of the section to reduce the pressureand create the partial vacuum therein.

After the sludge cake rotates out of the vacuum dewatering zone, thevacuum is automatically released by the valve 36 and the sludge cake, byits own weight, tends to fall off the filter screen. To assure that allthe sludge cake is removed, however, the scraper knife 97 scrapes anyremnants of it off before the screen 21 passes back into the body 1 l ofthe unit 10.

On its return trip to the roller 60, the filter media screen 21, in itsrun 71, is washed by a water spray unit 99 extending between the sidewalls 14 of the body 11. The spray water is also caught in the filtratepan 90 and passes out through the effluent ports 95.

It will now be recognized that a sludge concentrator system has beendescribed which obtains desirable, high solid content sludge which ischaracteristic of a vacuum-type system while eliminating the necessityof lifting solids and liquid out of a sludge tank with the vacuumsystem. As a result, the vacuum system can employ lower capacity piping,valving and auxiliary equipment, making system costs substantiallylower. In addition, with the system of the present invention, the sludgecake does not tend to slough off the filter media screen as it moves onthe drum, in contrast to the conventional system illustrated in FIG. 1,for example. Furthermore, the present system avoids classification ofsolids in the feed process; a common fault of conventional vacuum-typesystems.

The invention has been discussed primarily in the context of a sewagesludge concentrator system. Its principles are, however, equallyapplicable to the concentration of other solids from a liquid carrier;various ores, sand, or organic particulates for example.

In this light, it will be noted that the system described has a slightlyupwardly inclined upper screen run 70;

described as generally horizontal. Where other materials are beingtreated, the incline might vary down to 0,

depending upon the characteristics of the solid content portion of thematerial.

While the embodiment described herein is at present considered to bepreferred, it is understood that various modifications and improvementsmay be made therein.

What is desired to be claimed and secured by Letters Patent of theUnited States is: v

l. A sludge concentrator system for solid material in a liquid carrier,comprising:

a. drum means rotatable about a horizontal axis b. endless filter mediascreen means having a length substantially greater than thecircumference of said drum means, i

c. said screen means being trained around said drum means and idleroller means horizontally displaced from said drum means so that agenerally horizontal upper reach of said screen means is definedtherebetween, wherein said upper reach of said screen means is inclinedslightly upwardly in the direction of said drum means,

. baffle means bracketing said upper reach adjacent said idle rollermeans so as to contain .said liquid laden sludge on said upper reach. I

e. means for feeding liquid laden sludge onto said v upper reachadjacent said idle roller means,

f. said drum means being rotatable in a direction to draw the screenmeans from said idle roller means toward said drum means,

. whereby gravity de-watering of the sludge through the upper reach ofthe screen means takes place as the screen means moves toward said drum,and

. said drum having vacuum means therein for drawing additional waterfrom the partially de-watered sludge as it passes over said drum whereinsaid vacuum means includes valve means associated with said drum forcausing a vacuum to be effective on the surface of the drum only in afixed arcuate segment of the drums rotational cycle and wherein saidfixed arcuate segment includes a greater arc span of said drum than thefirst quadrant of said drum, measuring from the top of the drum in thedirection of its rotation but less than the first and second quadrantstogether.

2. The sludge concentrator system of claim 1 further characterized byand including:

a. sludge feed means adjacent said idle roller means adapted to feedliquid laden sludge horizontally onto said upper reach of said screenmeans.

3. The sludge concentrator system of claim 2 further characterized inthat:

5. The sludge concentrator system of claim 1 further characterized inthat:

a. said screen means is fabricated of a mono-filacharacterized in that:

a. said mono-filament screen means ment, woven material in a singlethickness. 6. The sludge concentrator system of claim 5 further includesopenings in the 50-500 microns size range.

unlnnn nor:

1. A sludge concentrator system for solid material in a liquid carrier,comprising: a. drum means rotatable about a horizontal axis b. endlessfilter media screen means having a length substantially greater than thecircumference of said drum means, c. said screen means being trainedaround said drum means and idle roller means horizontally displaced fromsaid drum means so that a generally horizontal upper reach of saidscreen means is defined therebetween, wherein said upper reach of saidscreen means is inclined slightly upwardly in the direction of said drummeans, d. baffle means bracketing said upper reach adjacent said idleroller means so as to contain said liquid laden sludge on said upperreach. e. means for feeding liquid laden sludge onto said upper reachadjacent said idle roller means, f. said drum means being rotatable in adirection to draw the screen means from said idle roller means towardsaid drum means, g. whereby gravity de-watering of the sludge throughthe upper reacH of the screen means takes place as the screen meansmoves toward said drum, and h. said drum having vacuum means therein fordrawing additional water from the partially de-watered sludge as itpasses over said drum wherein said vacuum means includes valve meansassociated with said drum for causing a vacuum to be effective on thesurface of the drum only in a fixed arcuate segment of the drum''srotational cycle and wherein said fixed arcuate segment includes agreater arc span of said drum than the first quadrant of said drum,measuring from the top of the drum in the direction of its rotation butless than the first and second quadrants together.
 2. The sludgeconcentrator system of claim 1 further characterized by and including:a. sludge feed means adjacent said idle roller means adapted to feedliquid laden sludge horizontally onto said upper reach of said screenmeans.
 3. The sludge concentrator system of claim 2 furthercharacterized in that: a. said sludge feed means including trough meansoverlying said idle roller means and adapted to direct liquid ladensludge onto said upper reach of said screen means in the direction ofsaid drum means.
 4. The sludge concentrator system of claim 1 furthercharacterized in that: a. said drum has a relatively large circumferencewhich is at least one-half of the length of the screen means.
 5. Thesludge concentrator system of claim 1 further characterized in that: a.said screen means is fabricated of a mono-filament, woven material in asingle thickness.
 6. The sludge concentrator system of claim 5 furthercharacterized in that: a. said mono-filament screen means includesopenings in the 50-500 microns size range.